U.S. patent number 5,143,049 [Application Number 07/498,711] was granted by the patent office on 1992-09-01 for pump for secondary circulation.
Invention is credited to Karsten A. Laing, Nikolaus J. Laing.
United States Patent |
5,143,049 |
Laing , et al. |
September 1, 1992 |
Pump for secondary circulation
Abstract
In a plumbing installation wherein hot water is piped from a
water heater or reservoir to a plurality of taps by a distribution
conduit, an improved recirculation circuit of limited power
consumption to continually pump small amounts of hot water from
said conduit back into said reservoir which comprises a low power
radial pump unprotected by a check valve against backflow, but
having a rotary impeller with linear radial vanes leading to an
annular output channel larger than necessary for maximum pumping
throughput. The oversized annular channel and linear vanes limit
the impact of any backflow upon the impeller and prevents its
operating as a tubine as the pump is subjected to back pressure
when a large amount of water is being drawn through the taps.
Inventors: |
Laing; Karsten A. (Chula Vista,
CA), Laing; Nikolaus J. (Chula Vista, CA) |
Family
ID: |
26807788 |
Appl.
No.: |
07/498,711 |
Filed: |
March 26, 1990 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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110192 |
Oct 19, 1987 |
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Current U.S.
Class: |
122/13.3;
137/329.1; 137/563 |
Current CPC
Class: |
F04D
13/16 (20130101); F04D 29/242 (20130101); F04D
29/445 (20130101); F24D 17/0078 (20130101); Y10T
137/6184 (20150401); Y10T 137/85954 (20150401) |
Current International
Class: |
F04D
13/16 (20060101); F04D 13/00 (20060101); F04D
29/24 (20060101); F04D 29/44 (20060101); F04D
29/18 (20060101); F24D 17/00 (20060101); F24H
001/00 () |
Field of
Search: |
;137/563,565,329.1
;126/362 ;237/19,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bennet; Henry A.
Attorney, Agent or Firm: Charmasson; Henri J. A.
Parent Case Text
PRIOR APPLICATION
This application is a continuation-in-part of copending application
Serial Number 07/110,192 filed Oct. 19, 1987.
Claims
What is claimed is:
1. In a plumbing installation wherein hot water is piped from a
reservoir to a plurality of taps by a distribution conduit, and
wherein the distal end of the conduit is connected to the reservoir
through a centrifugal recirculation pump protected by a
backflow-inhibiting check valve, said pump having a rotary impeller
directing water from the impeller hub region toward a peripheral,
annular channel leading to an outlet port, wherein said impeller is
attached to the rotor of a spherical gap electrical motor, said
rotor and impeller being rockingly held against a single, central
ball-bearing by magnetic coupling between the rotor-driven pole
ring and the driving pole ring of the motor stator, the improvement
comprises:
deleting the check valve; and
limiting the effect upon the pump of any backflow created by the
drawing of hot water through the taps, including increasing the
size of the peripheral channel.
2. The improvement of claim 1, wherein said step of limiting
further comprises fitting said pump with an impeller having
radially linear vanes.
3. The improvement of claim 2, wherein said step of increasing the
size of the peripheral channel includes reducing the diameter of
said impeller.
Description
BACKGROUND OF THE INVENTION
This invention relates to hot water distribution systems and more
specifically to a recirculation pump used to maintain a flow of hot
water throughout the distribution system in order to provide
instantaneous hot water at each tap. Since the recirculation system
needs only to draw a small amount of hot water from the
distribution unit in order to make hot water immediately available
to the various taps along the distribution system, the
recirculation can be achieved with a smaller gauge of pipe than
those used to supply the taps and a low throughput pump. Therefore,
a low throughput pump with approximately 10 watts of power could be
used in the recirculation circuit. However, when a large amount of
hot water is drawn through the taps, the recirculation pump is
subject to a substantial drop in input pressure amounting to up to
ten times the normal working pressure of the recirculation pump. If
the pump is not protected by a check valve the resulting backflow
causes the recirculation pump to act as a turbine rotating at a
much higher speed than the normal rated speed of the pump. Due to
the large calcium buildup which may be expected in hot water
circuits, the recirculation pump should not use any shaft and
bushing with narrow clearance which can seize under calcium
deposits. It is preferable to use a pump with a free-tilting
spherical rotor-impeller mounted on a small ball-bearing as the one
disclosed in U.S. Pat. No. 3,803,432 Laing. This pump and other
types with equivalent performance can be damaged by high speed
spinning due to backflow. It thus becomes necessary to install a
check valve in series with the recirculation circuit to protect the
pump. This in turn requires increasing the power of the
recirculation pump to 35 to 50 watts in order to overcome the
resistance of the check valve This added power may increase the
electric consumption between 200 to 300 kilowatt hours per
year.
There is need for an improved recirculation unit which would allow
for the elimination of the check valve while limiting the effect of
any backflow on the low power recirculation pump.
SUMMARY OF THE INVENTION
The principal and secondary objects of the invention are to provide
an improved, low power hot water recirculation pump which is immune
to damage due to backflow caused by the drawing of large amounts of
hot water through the distribution system.
It is also an object of the invention to limit the energy
consumption of a hot water distribution system by providing instant
hot water at each drawing tap while limiting the amount of power
necessary to permanently circulate small amounts of hot water
through the system.
These and other objects are achieved by means of an improved
low-recirculation centrifugal pump which has an impeller with
radially linear vanes leading to an oversized annular output
channel which together limits the impact of any backflow upon the
impeller.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 illustrates a water heater distribution and recirculation
system of the prior art;
FIG. 2 is a perspective view of the rotary impeller and output port
of a conventional centrifugal pump;
FIG. 3 is a front elevational view thereof;
FIG. 4 illustrates the water heater distribution and recirculation
unit improved in accordance with the invention;
FIG. 5 is a perspective view of an improved centrifugal pump water
assembly;
FIG. 6 is a front elevational view thereof; and
FIG. 7 shows, in sections a pump motor and impeller assembly
improved according to the invention.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The state of the art in other hot water distribution systems with
continuous recirculation is illustrated in FIGS. 1-3. In FIG. 1,
there is shown a water heater 1 with a hot water distribution
circuit comprising a pipe 2 leading to a plurality of taps 3
representing showers, tubs and sink faucets. Hot water is drawn
from the distal end 4 of the hot water distribution network by a
centrifugal pump and returned to a lower region of the water heater
by a pipe 6 having a gauge smaller than the pipe 2 leading to the
taps 3. The pump 5 is of a low throughput type protected by a check
valve 7 against any backflow which may be caused when hot water is
drawn at the taps. Typically, the recirculation pump 5 has a power
of 40 to 50 watts sufficient to overcome the resistance of the
check valve 7. The impeller and housing of a typical centrifugal
pump 5 are illustrated in FIGS. 2 and 3. The driving motor and
associated coupling have been omitted. The impeller 8 has a
plurality of back-bent vanes 9 which when driven clockwise direct
the flow of water emerging in the hub region 10 from the inlet pipe
11 toward an peripheral, annular channel 12 leading to the output
port 13.
Due to the fact that calcium deposits are frequent in hot water
systems, it is preferable to use a pump which does not have any
close tolerance impeller bearing surface such as the type of pump
disclosed in U.S. Pat. No. 3,803,432 where the impeller and rotor
are suspended on a ballbearing assembly, which patent is hereby
made part of this specification by reference. This last described
type of pump could be damaged by backflow which occurs when the
input pressure of the pump drops as water is being drawn from the
taps 3. The resulting backflow illustrated by arrow 14 in FIG. 3
acts upon the curved vanes 9 of the impeller causing the pump to
work as a turbine. When one considers the fact that the drop of
input pressure can be up to 100 times the working pressure of the
pump, one can appreciate the damage that may be caused in the
fragile bearing of the recirculation pump. The check valve 7
eliminates any chance of backflow. It should be understood that if
the effect of backflow could be reduced, and the check valve 7
eliminated, the power of the recirculation pump 5 could be reduced
to approximately 10 watts for a typical domestic hot water
installation. This will result in a substantial power saving over
time.
Such an improved system is illustrated in FIG. 4 which is
distinguished from the installation illustrated in FIG. 1 by the
absence of the check valve 7 and the increased dimension of the
output port 15.
The pumping mechanism has been modified to limit the effect of
backflow by using an impeller 16 having linear rather than bent
vanes 17. More significantly the annular channel 18 has been
greatly enlarged by, in the case of the embodiment illustrated in
FIGS. 5 and 6, reducing the diameter of the impeller 16. The size
of the output port 19 has also been increased. It can be understood
that these modifications to the pump may result in a drop of
efficiency and throughput. However, this drop in efficiency is
largely compensated by the fact that the effect of any backflow
illustrated by arrow 20 has little or no effect upon the vane 17,
thus avoiding the high speed turbine action inherent to the pumps
of the prior art. As illustrated in FIG. 7, the annular channel 21
surrounding the impeller 22 and the output port 23 have much
enlarged cross-sections compared to the annular channel and output
port illustrated in FIG. 1 of U.S. Pat. No. 3,803,432.
While the preferred embodiment of the invention has been described,
modifications can be made and other embodiments can be devised
without departing from the spirit of the invention and the scope of
the appended claims.
* * * * *